Page 13 - Volume 11 Number 8

AC technicians pull Freon out of an AC system and store it. The Freon is filtered during this process so it’s safe to be reused. These machines have built-in sensors to indicate when the filters need to be changed.
Anyone buying Freon must (a) be licensed to do so, and (b) be very discerning. My supplier weighs each incoming cylinder of R12 before accepting it to ensure it’s not tainted. Freon is heavier than air; if any air is cut into the Freon to dilute it, the cylinder won’t weigh enough. Watch out for Freon substitutes, they can become highly corrosive. They often contain methyl chloride which turns more acidic with less moisture than R134a or R12.
FR12, also known as FrigC, sometimes creates confusion. FR12 is R134a with butane added; it’s used in older cars. It comes in a white cylinder, which is the odd part. Refrigerant bottles are color coded and white is reserved for R12, sky blue is for R134a. Once I was buying R12, but got a cylinder of FR12 by mistake. When I looked closely I saw “Tetrafluoroethane” on the cylinder which threw me for a loop and wondering what R134a was doing in a white cylinder. Well, it’s a funky cylinder, constructed upside down compared to R12 and R134a. These days R12 is becoming harder to come by. Those white cylinders are a sight for sore eyes, provided it’s pure R12 and not FR12.
Mercury and Microns
A vacuum pump is used to evacuate the Freon from a system, then a stronger vacuum is applied and left on the system for a period of time. Moisture boils more readily under a vacuum. This is how moisture is purged from AC systems – the moisture is boiled away and the dry air is pulled out by vacuum.
The King Air manual calls for a vacuum pump that pulls at least 29 Hg (inches of mercury) and 125 microns. A proper AC machine in good condition meets this criteria. But on occasion, I have used a vacuum pump pulling 250 microns
AUGUST 2017
KING AIR MAGAZINE • 11